Radio telephony



H. S. POLlN RADIO TELEPHONY July 11, 1933.

Filed May 21, 1929 5 Sheets-Sheet 1 a gmemtoz ElrZe rilifgliw,

H. S. POLIN RADIO TELEPHONY July 11, 1933.

Filed May 21, 1929 5 Sheets-Sheet 2 ,Lmhkm WLMAINW H. S. POLIN.

RADIO TELEPHONY July 11, 1933.

Filed May 21, 1929 5 Sheets-Sheet 3 H. S. POLIN RADIO TELEPHONY July 11,1933.

Filed May 21, 1929 5 Sheets-Sheet 4 gwmnto'o July 11, 1933. s, POLIN1,917,995

RADIO TELEPHONY Filed M ,21, 1929 5 Sheets-Sheet 5 ml l l m" gwuomloc UNLWAQWMMWM Patented July 11, 1933 UNITED STATES PAT ENr- 'oFF- cE:

HERBERT S. POLIN, OF SAN FRANCISCO, CALIFORNIA, ASSEGNOR,.BY DIRECT AND'AIESNE A SIGHMENTS, T0 INTERNATIONAL RADIGPHONE CGRPORATIQN, OF WASH-ENGTON, DISTRICT OF COLUIQBIA, A CORPORATION OF BELAQVABE RADIOTELEPHONY Application area May 21,

My invention relates to automatic te1e phony.

More specifically, it relates to a system of means for tuning thetelephone apparatus of the calling subscriber to the wave length of thesubscriber called. r

Other objects and advantages of my invention will be apparent from thepresent specification in connection with the drawings attached thereto.

in said drawings:

Figure 1 is a diagram showing one type of circuit which may be used atthe trans mitting end of a subscrihers station.

Figure is a diagram of a calling dial embodying variable condensers inits structure.

Figure 3 is a diagram showing, in front.

. e evation, some of the mechanical and electure as Figure 3, but withthe parts in a different position.

Figure 3" is a section on line b7) of Figure 3.partiyin elevation.

Figure 3 is a diagram illustrating the operation of the contact armshown at the right of Figure 3*. This figure is a section on line c-c ofFigure 3", looking in the directi on of the arrows.

Figure 1 is a diagram showing an alter native circuit which may beemployed, as the transmitting means.

Figure 5 is diagram of a circuitwhich may be used as the receivingmeans.

Figure 6 is a diagram of a portion of a 9 circuit which may be employedto actuate act .ductor24. Inasmuch as one part of the grounded part of1929. Serial No. 364,838

is connected to, and formsa part of, the c1r'- cuit shown in Figure 5.,and shows the connec trons relating to the relays V V and'V3. of

Figure 5.

Referring now specifically to Figure 1,

the transmitting portion of the subscribers station comprises athermionic tube 16, hav' ing a cathode 18 heated by any suitable means21, a grid 19 and a plate 20. A telephone induction coil or itsequivalent; comprising coils 63 and 59 Wound upon core 62, is provided,the primary coil 63 being connected to the microphone 65 by meansofconductors 64 and 67-, a source of current 66 being interposed inconductor 67, as shown. One end of the secondary coil 59 is connected tothe conductor 4-2, which is grounded at 60. The other end ofcoil 5 9 isconnected to the grid v 19 through a path including conductor 58, gridleak 55, conductor 56, coil 23and 0011- cathode 18 is also connected tothe ground through conductors 61, hland 60, this pro-- vides a circuitwhereby any speech currents originating in-the micropho'necirc'uit will"produce potential variat1ons or" the grid 19 with respect to thecatho'delS. A by-pass condenser 22 is connected to one end of the 1 coil23 by means of conductor 56, and to the the cathode 18 through"conductor 57. i A dial 10, embodying in its structure a plurality ofcondensers 14, preferably ten in number to correspond to the ten digitsof the arabic system of numbers, is connected into the circuitasfollows? Each condenser 14, here shown as a fixed condenser, has oneterminal connected to the central shaft 118 of the dial, the othertermi; als being connected to the ten contact points 31 arranged uponthe periphery of the: dial,

as shown. Thesecontacts 31 are arranged scribed, to the stationarycontact 25, connected to conductor 26 as shown. Assumin that such waythat oscillations will be set up thereby in the well known way, thefrequency being determined by the inductance of coil 23 and the capacityof the condenser 14 at that time in circuit.

The energy producing these oscillations is derived from the source ofcurrent 36, here shown as a high voltage B battery, although it will beunderstood that this showing is purely diagrammatic and any suitablesource of power may be employed. 7

It willbe further understood that, while, for convenience ofillustration, various distinct sources of current are shown, in practicemany or all of these may be. combined so that all the power is derivedfrom a single source, as is customary in radio circuits. This however,forms no essential part of the present invention, and many ways ofaccomplishing it are well know in the prior art. The negative terminalof the source of power 36 is connected to the cathode 18 by means ofconductor 61, and the positive terminal leads to the plate 20 throughcoil 32 and conductor 26, as shown. A by-pass condenser 35 connects theterminals of the: power source 36 to each other through conductors 33,34 and 61, as shown, and serves as a loweimpedance path for highfrequency currents.

The coil 32 is coupled magnetically to coil 37, one end of which isconnected to the grid 53 of a second thermionic tube 17, through theconductor 38, while the other end of this coil is connected to thecathode 52 of the tube by means of conductor 39, C battery 40 andconductors 41, 42 and 50, in the order named. The cathode 52 of thistube is energized by a source of power 51 in a usual way. The outputcircuit of the second tube 17, comprises a source of power 48 and a coil45 connected inseries between the plate 54 and the grounded conductor42, by means of conductors 46. 47 and 49, as shown. The coil 45 iscoupled to a coil 43, which is located in the antenna circuit,comprising conductors 42 and 44 and the said coil 43.

A hook switch 28, controlled by the weight of a telephone receiver inthe usual manner, is provided to close an alternative circuit betweenthe grid 19 and plate 20 of the tube 16. this circuit comprising part ofconductor 24. variable condenser 30, conductor 29, switch arm 28,contact 27 and conductor 26. The variable condenser 30 is mechanicallycontrolled by means operated by the dial, which will be more fullydescribed hereinafter, and indicated diagrammatically by the dottedlines in Figure 1.

The purpose of this arrangement is to adjust the rotor of condenser 30into a position corresponding to the last digit of the sum produced byadding the digits of the number which has just been called by thecalling subscriber. The purpose of. this arrangement will be discussedfully hereinafter.

Three different types of dials are indicated respectively at 10, Figure1; 12, Figure 2; and 13, Figure 4. The dial 10, as already mentioned,comprises a plurality of fixed condensers 14 embodied therein; the dial12 is similarto the dial 10, except that the condensers 15 embodiedtherein are Variable; and the dial 13 is the simplest of all, andcomprises merely a single contact upon its periphery, .connected to theshaft 118by means of conductor 113. The purpose of the diaLof whatevertype it may be, is to control the frequency of the radio energy emittedby the calling subscribers station during the signaling period. Thedials 10 and 12 accomplish this by virtue of the variation of capacitywhich is produced in. the oscillating circuit upon the actuation of thedial, while dial 13, on the other hand, controls a set of crystaloscillators directly governing the frequency of the radio currentsproduced.

Each of these dials, 10, 12 or 13, regardless of its electricaldifferences, is mechanically substantially identical, and is illustratedin detail in Figures 3, 3, 3 and 3.

Furthermore, each dial 10, 12 or 13 may control the impression of a lowfrequency ringing current on the emitted wave. This is accomplished bythe connections shown in Fig. 4, where the dial is arranged to control aswitch 155, 157, to open the switch when the dial is ata normalposition, and to close the switch to send the low frequency ringingcurrent, when the dial is away fromthe normal position as described morein detail below. i

Referring now specifically to said Figures 3, '3, 3 and 3, the dialmechanism there illustrated comprises a flat disc 335 having ten ratchetnotches cut-therein, as shown at 344, and also an additional notch witha curved bottom, 346. These notches cooperate with a pawl 313 carried byan arm 311 to which it is pivoted at 312. The arm 311 itself is pivotedat 310 toa stationary portion of the housing, 339, and is forced to theleft by a spring 347 so that normally the pawl 313 is held against theperiphery of the disc 335. The pawl 313 is urged downwardly by a spring315 connected at one end to a pin 316 on thearm 311, and at its otherend to the pin 314 on the pawl. A stop 317 secured to the edge of thedisc 335 and movable length #9. The pawls 327 and 328, when the disc 335is in its normal position, will pawls 327 and 328, and releasingtlierlisc 331,-

which thereupon returns to its normal position in response to the spring332, and thus restores the entire mechanism to its normal position readyfor anew call.

Referring now to Figure l, there is illustrated another form' of circuitembodying my invention. This circuit differs from that shown in Figure1, in that it is far more sensitive, selective and powerful, theseadvantages being obtained by substituting crystal oscillators for thecondensers in the dial of Figs. 1 and 2. and by substituting screenedtheZero position should be insufficient, any

grid tubes for the ordinary thermionic tubes used in the Figure 1circu1t.

- In this form of embodiment the dial is simplified electrically toinclude merely a single contact element 113, the outer end of Which isarranged to make contact with the stationary contacts 88 to 97inclusive, arranged adjacent the circumference of the said dial in muchthe same way as the contact'25 of Figure 1 cooperates with'the dialcontacts 31 of that figure. It will be understood, of course, that thestationary contacts are not all engaged by the dial contact 113 everytime said contact passes'a stationary contact. but that the dialmechanism illustrated in Figs. 3, 3a, 3?) and 36- will operate as in theother modification to'cause a temporary connection with only thatparticular stationary contact which corresponds to the highest digit towhich the dial has been turned upon each actuation thereof.

.It will also be understood that if the friction in the dial whichretards its return to of the usual known retarding means may be providedto slow down the return of the dial,

in order to provide a sufiiciently long time .of connection between thesaid rotating and 'stationary contact, in orderthat the wave filtershereinafter described may have sutii- "wires 98 to 107 inclusive to theconductor 108, which is connected to earth by conductor 109, as shown.Another conductor 11-1- leads from the shaft 118 of the said dial to thegrid of a screen grid tube. A switch icomprising lever 155 andstationary contact 157 is placed into position to cooperate mechanicallywith the dial 13, as illustrated. diagrammatically at 15 1. This isintended to show that by some mechanical connection between the shaft118 and the element 15st, the switch lever 155 will be removed from thestationary contact 157 whenever the dial is at normal position, but thatthe said switch 155157 will be closed whenever the dial is away from itsnormal position, for instance, in the position shown, wherein contact 88is connected to the movable contact 113, and

, therefore to the grid 115 of the screen grid tube. V

This switch 155, 157 controls the input circuit of a low frequencyringer 161, which comprises a source of power 158, connected to theswitch contact 157 by a conductor 160, and then through movable switchelement 155 and conductor 156 to the ringer, andback to the source ofpower through conductor 159. The output side of this ringer is connectedthrough conductors 162 and 163 to the primary coil 164- of a transformercomprising also a core and an output winding 166.

l? fez-ring bar-l; now to the screen-grid tube which comprises grid11.5, screen-grid-127, cathode 116 and plate 117, the grid 115 of thistube which is, as already stated, connected to the shaft 118 of the dialis also connected through conductor 121, coil 122, conductor 123, gridleak resistance 124v and con 'ductor 125 to the common ground conductorgrid 127 is connected through conductor 128 to an intermediate potentialpoint of a source of power 153, which may be a B battery or a similarhigh voltage power source. A condenser 120 is interposed between theoathode 116 and the conductor 128, as shown.

The plate circuit of this tube comprises a source of high voltage power153, the negativeterminal of which is connected'to the ground conductor108 by a conductor 152, the positive terminal of said power element 153being connected through a coil 131and conductor 132 to the plate 117. Acircuit comprising conductor 120, condenser 118 and conductor 119 formsa shunt between the grid 115 and the platc117, as illustrated. Thisscreen-gridtube with its connected circuit, serves solely to amplify theoscillating currents conducted by the wave filters 68 to 77 inclusive,and takes no part in the functions of signaling or talking.

A microphone 173 of any desired type is connected through a conductor172, source of power 171, conductor 170 and primary coil 169 of atransformer or induction coil, back to the microphone 173, as shown. The

said transformer or induction coil has a. core output Winding 167 isconnected in series with -the output winding 166 of the signalingtransformer through a conductor 177 to the negative terminal of a sourceof energy 140,

which furnishes a negative bias to the grid of the second thermionictube, shown in Figure 4, to which it is connected through the conductor148, coil 138 and conductor 134, as shown,

The grid 135 is connected to-the plate 117 of the preceding tube bymeans of conductor 132, condenser 133 and conductor 134., as shown.Thus, the coils 131 and 1338 together with the stopping condenserconstitute what is known as an impedance coupling between the outputcircuit of the first screengrid tube and the grid circuit of the secondtube.

The'screen grid 136 of this tube is connected by conductor 139, on theone hand, to an intermediate potential point of the high voltage powersource 153 and, on the other hand, is connected through a stopping,condenser 141 to the conductor 147, which connects the cathode 143 ofthe said tube tothe ground conductor 108. The cathode 1430f this tube isenergized by any suitable means 142. The plate 137 of the tube isconnected to the positive terminal ef the high voltage source 153through conductor146, coil and conductor 144. The coil 145 is coupledinductively to the coil 110, one terminal of which is grounded throughconductor 109, and the other of which is connected to the antenna111.-

A hook-switch 176 is illustrated diagrammatically and is so arrangedthat when the receiver is removed from the'l'iook, the switch arm 176will be connected with the stationary contact 175, which will close apath co1-n prising winding 166, conductor 174, switch arm 17 6 andcontact 175, so as to short circuit saidi winding 166 whenever thereceiver is removed from the hook. T V

The operation of the circuit shown in Figure 4 is as follows: Uponactuation of the dial to call the remote subscriber, said dial willactuate the contact 113 to close one of the crystal circuits, when thesaid dial is released by the finger of the subs )riber making the call.Thcreupon the corresponding wa ve filter of the-series 68 to 77, whichare assumed to have different fundamental frequencies, will' conductoscillations which will heimpressed" upon the grid 115 of thefirst'tube. This tube will amplify said oscillations very strongly, andin turn theamplified oscillations will ,berimpressed upon the grid 135of the s cond tube, through the interposed impedance coupling 131, 133and 138. This tube in turn will amplify these oscillations andimpress'them upon antenna. 111 through the output coil 143, whichisvcoupled to the antenna coil 110. During all this time, the lowfrequency ringer 161 is producing low frequency impulses near or "belowthe lower limit of audibility, which are impressed upon "the inputWinding164 of thetransformer, whose 135 of the second tube, therebyimpressing oscillations of a ringing frequency upon -said output winding166 is connected to thegrid E grid at the same time that the wavefilters condu ct their own high frequency oscillations to said grid. '1

Thus, high frequency oscillations modulated by the ringing frequencyareimpressed finally upon the antenna 111 and transmitted through spaceto the various receiving Istations. 7 I

The low frequency rlnger 16:1 w1ll,'of

course, continue to .be'encrgize'd so long as the dial 13 is away fromits normal position, and will automatically stop producing low frequencyoscillations when the dial 13 re- 1 cuit the output winding 166 of theringing I transformer, so toremove its: needless, inifpedance from thetalking circuit, until such time as the receiver is again-returned tothe hook and conditions are returned toreadi-ness for signaling thenext'numberto be called. 7 Referring now to Figures 5 and 6, there 1sindicated diagrammatically in these figures one arrangement which thereceiving station may employ. The circuit comprises an an-" tenna 182-connected to the ground through coil 181 and conductors and 178, asshown.

The energy received by the antenna is trans- ,mitted to the coil-183 byinduction,="'and thence passes through conductor 184 to the grid 198 ofthe screen grid tube-221.

- The other terminal of the coil 183 is connectcd to the negativeterminal of asource of power 185, which furnishes a negative bias to thegrid 198, and-the other terminal of which is connected tothegrounrlconduo tor 178, as shown. Aby pass condenser 191 is shuntedacross the terminals of said source by means of the'conductors wean-d192, which connect it respectively to the conducters 193 and 178. Thecathode 197 is pro? vided with a suitable energizing means 196 and isconnectedto'the'ground conductor 178 through a conductor 17 9.Thescr'ee'n grid 199 is connected through a conductor 194 to an in:

termediate point of ahigh potentialpower source 219, thenegativeterminal of which I is conne'ctedt-o the ground conductor 178 throughconductor 220,andthe,positiveitere minal through theW'inchngQOZof aftr'ans-x former, and" conductor 201, to the) plate ofthe' said'tube. v

A by pass condenser 1951s connected between thercathode 197 and theconductor194 leading to the screen .grid 199, as shown. These elementsconstitute the input and output circuits ofthe screen-grid tube 221, theinput side of'which is tuned broadly by Ineansof the coil 183 only, andthis tuning 'may be made sharper by means of the condenser 186, which isconnectible across the said coil 183 through conductors 187 and 190, andinterposed hook switch'188, 189, which is so arranged that this switchwill be closed when. the receiver is lifted from the hook. Coil 1'83 andcondenser 186 are tuned so as to have a receptive range suflicientlywide to pick up any wave length to whichthe circuits associated withcoils 231, 241, 251 and '261 are tuned.

202 and 204 may be arranged upon the core 203, as shown, although itwill be understood that core 203 must be of a'high frequency type, thatis, the lanimations must be of very thin good quality iron orsteel, andif the frequencies are sufficiently high the core may be .omittedentirely, thus constituting a transformer coupling between the plate 200of thefirst tube 221 andjthe grid206 of the second tube 222. a

The output of the tube 222 comprises the winding 209, one terminal of.which is c011- nected through conductor 208-to the plate 207 of the saidtube,'and the other terminal of which is connected through the conduc'tor 217 to the positive terminal of the source of highvoltage energy219. c r

' Coupled to the winding 209 are a'series of windings 231 241, 251 and261respectively, each of which supplies the input energy for; acorresponding one of a series of there mionic tubes 240, 250, 260 and 270. The first of these tubes 240 constitutes the amplifying means for thereceived 1 talking currents, While the remaining three, 250, 260 and270, are provided for signaling purposes only. Consequently a hookswitch indicated at 227,

228 is provided and so arranged that when the receiver is lifted fromthe hook the.circuit will be interrupted, between stationary contact227and movable contact 228, wherebythe energy from the power source'219arrivingthrough conductor 215 can not pass to conductor 229 when thereceiver is oil the hoolnithus avoidingany needless-flow of energythrough; thesignaling tubes, except.

Each coil 231, 241, 251 and 261, and their respective condensers 233,243,253 and 263 and associated thermionic tubes form different,individually pre-tunedcircuits. The circuit associated with coil 231 istuned to the talking wave length of this particular station and would bethe same wave length as that selected by the dial 10, 12 or. 13 at theend of the dialing operation. The circuits associated with coils 241,251 and 261 would be tuned to different Wave lengths, each the same asthe wave length representing the calling wave lengths for thisparticular station, as determined by the dialing of the callingsubscriber. station represented 'in Figs. 5 and 6is station number 357,for example, the respective circuits associated with coils 241, 251 and261 will be tuned, respectively to the Wave lengths sent from circuitsestablished through contact points 3, 5 and 7 by the dial at the sendingstation.

The tube 240 which amplifies the conversation currents is connected tothe output winding 231, which is connected to the cathode 237 throughconductor 239 and'to the grid 235 through the grid condenser 234, andgrid leak 232, as shown, a'tuning condenser 233 being connected inparallel with the coil 231. The cathode 237 of this tube is onergized bysuitable means 238. The receiver 224 is connected as usual in a circuitcomprising the conductor 215, leading from the positive terminal of thesource 219 and passing from the receiver 224 to the plate 236 throughthe conductor 225.

The. signal operating tubes 250, 260 and 270 are coupled to the winding209 in a manner similar to that of tube 240, each tube having acorresponding winding 241, 251 and That is to say, if the 261, connectedto itsrcspective grid 245, 255,

265, through the grid condensers 244, 254 and 264, each grid condenserbeing shunted by a corresponding grid leak 242, 25 2, 262, and each]winding 241, 251 and 261 being shunted by a tuning condenser 24.3, 253,263 rcspectively, and being connected to the cathode 247, 257 and 267through conductors 249, 259 and 269 respectively. Each cathode isactuated through a suitable source 243, 258 and 268. The plate 246 isconnected to the positive terminal of the source 219 through a conductor271, in which is interposed a vibration relay V thence through a 0011d11ttor 229, through the hook switch 228, 227 and conductors 226 and 215 tothe said positive-terminal of source 219. Similarly the plate voltage,is supplied to plates 256' and 266 through conductors 272, 273 and 274,27 5, wherein are interposed the corresponding vibration relays V andV,,, respectively,

The vibration relays and their circuits are illustrated in Figure 6,although it willbe understood that Figure 6 really forms apart,l1ere,-other than the ststenr 'eral a reed is set into vihr:

siderflhle or V,

. the 'ontucts thence throng 1 type, wherein a contact is establishedonly 'when current of the proper t supplied thereto. Such relays are Win the art and need no further description t that in genron by the fieldproduced by an alternatingor pulsating current in u coil and thisvibration becomes conwhen the requency otfthe current near the naturalfrequency of vibretionotf the reed.

The relay V controls ercircu conmrisingr conduc'lor 27S, source of en 'ytor 280,clectromsgnct a r this circuit being cmurocted to 276 and 277or" thou-clam so t incgrnes'; 281 hecoznes c ner, cont-nets areactuated. ll hen V net 281 heroines energized it will armature and causeitto e W contact 283. A dash not retard the return motion at the s Therelay V iseriuctly lil-te the and inturnmmtrols a circuit corms-risingconductor 282. miniature cert tor 28-1 clectromsgnet 3 the 9292',conllru'tor 290,

to the conflicts r a conductor source of" energy 291, and this circuitbeing connected 288 and 289 controlled by the lay V I 11 srmutru'e roerstes withlhe'eler tromegnet 293 and is retarded by :1 dash notiT.these pa s heinp; similar to the corresponding p: fl'S sud of the firstrc luv. hen the clectrmnnc'net 293 is encr-' sized by current flowing:from the source 291, and when the relay V5 is closes and simultaneouslyrelay armature is with 283. the zirnmture v-J bv eleci'romsgnet and tlui V be ceiniccted with said will establish :znel'herri ductor 29:),electroum 3GP smlrce of energy 2-302, ceud' 360 and oi 'l conflu mature295. it, th nected to the srmstu L cusl r the rclay'V; be c which isconnected tothe eonductcrs 30?, 308 will be closed and the signal oi?the called subscriber (not shown) will be actuated for a perioddepending upon the charac eristics conduc-Q 1 curing of the erinsture305. v I

flhe operstlon of the c1rcu1-ts shown 1n Figures 5 and 6 is as follows:I

l Vhcn an impulse of radio fr q with" in a certain range of Wavelengths, strikes the antenna 182, the resulting currents proof the dashoot306, which retards the mot-ion 'duced in coill83 Will be amplified atradio frequency, first by the screen-grid tube 221,

turn to the ourseparatewindings 231, 241,;

and 261, connected to the respective tubes 2&0, 250, 260, 270. Each ofthese'tubes as described has s detector circuit attached to the gridthereof, wnereby' the radio frequency impulses ZUYG-COHVGTtGd intoiuldiofrequency impulses in the corresponding platecircuits.

As stated in the description of Figure 4, the period that the dial isbcmg opereted, ringing currents of low frequency are superimposed uponthe high frequency impulses emitted by the transmitting antennu andthesehigh frequency currents thus modulated are impressed simultaneouslyand successively on coils 241, 251 and 261, as dcterlnincd by thedialing. The successive calling wavelengths are each di'lterent, and

they are such the respective wave lengths to which the circuitsassociated With 241, 251

or 261cm tuned, and are sent in properse ({HQIICC, the bell will be rungat the station" 1 7 v wv shown in Fig. l he final wavelength1mgiresscdon tl'ris station is the Wave length filor this station and is that towhich 231,

2 33 and 220 are tuned. In the; circuits of the tubes 250, 260, and 270,they will 'trzwerse the vibratory relays V V V and if the input circuitof any one of these tubes is tuned in reson sncc with the high frequencyimpulses received the magnitude of the received curre cultu cluste thevibrutory releyi f the impulse be of such frequency that rclsy'V oractuated without actuating IV however no siq'n'alin will result for r tJb 3 although the contuctsof relay V or V3 might (llGSQ-XlySElll theywould not complete 011'- cui which include the electromagnets 293 or L03inasmuch as the circuit ofthe, first relay iso'pened between'285 and283. There'- fore, it is essential that-the relay V be the 5 to operate,it the signaling'means is to actuated. This requires that the firstimpulsesent outmust be of the frequencyto x'vhleh the tube 250 istuned,in order that suiiicient power may be fed to relay Vy to bi contactstogether. W hen this conit will be sutlicientin that purticulercirurtionhas been established the clectroniagnet28l will be actuated, and this inturn will close the contact rat'283ywhich will remain closed after theencrgiza'tion of 281 ceases for such period as the dash pot 286 isadjusted.

that in turn it will cause the electromagnet 293 to be energized duringthe remainder of l the period before the armature 2 85 breaks connectionat 283. 1

.. Finally, if a third "impulse be received by the antenna 182, andlikewise this be of a frequency for which the circuit or tube 270 istuned, the last electromagnet 303 will be energized in a similarway, andit in turn will close .the ringing circuit and the bell of thesubscriber being called will rin WVhen he lifts up his receiver 22%, hewill automatically breals the signaling circuit,

and thus disconnect the three signaling tubes from the circuit, andlikewise he will throw the condenser 186 across the input coil 183, thussharpening the tuning very considerably and concentrating all thetalking energy into thereceiver circuit, namely, the circuit controlledbytube 2 10. V v

lVhile for simplicity and convenience of illustration two differentreceiver hooks 189 and 228 have been shown, it will be understood thatthese are merely diagrammatic showings, and that both, in fact, aremerely switches which are controlled by a single hook, namely, of oneupon which the receiver 224 is supportedwhen not in use. It will also beobvious fronrthe circuits shown, that unless impulses of the properfrequency are fed in proper sequence, and

. within predetermined limited times, to the three relays V V and V nosignal will be produced, although one or more or even all of therelaysmay be actuated in improper sequence.

These frequencies are, of course, determined by the dials 10, 12 or 13,as. the case may be. It will also be understood that while only threerelays of the types-V V V are illustrated, it is possibletouse anydesired number, dependent upon the number of digits in the largesttelephone number to be called.

It is also obvious, of course, thatif greater power be required at thetransmitting end, or greater sensitivity at the receiving end, this mayreadily be provided by correspondingly increasing the number ofthermionic tubes employed.

A further feature of the system employed in accordance with thisinvention is that the tube 240, over which the actual talking is done,has its input circuit tuned to a frequency corresponding to the lastdigit of the number obtained by adding all the digits of the calledsubscribers own telephone number.

For example, if his number were 153, the sum of the digits would be 9and thelast figure of dial 10 has been moved in that case. and thisproduces radio frequency currents of that frequency whenever the hookswitch 28 has risen into contact with the stationary contact 27.Therefore, the calling subscriber auto matically. tunes his transmittingstation to the frequency for which the receiving station he is callinghas been adjusted. Thisis accomplished as is shown diagrammatically inFigure 1, and as shown more in detail in Figure, 80.

It must be understood, of course, that the various circuitsandinstrumentalities illustrated are purely diagrammatic in nature, andthatin practice necessarily refinements and details will need tobeconsidered which form no. part of the invention itself, but are inaccordance with ordinary telephone and radio practice.

It will also be understood that many deviations fromthe structures andcircuits illustrated will occur in practice without departing from thespirit of the invention, which is defined by the following claims.

\Vhat I claim as my invention is:

1. A system of radio telephonic communication comprising a series ofsubscribers stations, each having calling means including a manuallyoperated dial capable of emitting a sequence of impulses of certainfixed wave lengths, and in an order determined by the movements of thedial, the movements of the dial also simultaneously establishing afrequency. on which conversation can be carried on, and areceiving-circuit which isresponsive, at each station, only to aparticular one of such sequences, whereby the signal of only thatsubscriber who is called will be operated.

2. A system of radio telephonic communication comprising a series ofsubscribers stato the same frequency as that established by themovements of the dial at the sending stathis sum would therefore also be9, or if tion.

3. A system of radio telephonic communilength for ringing, and in anorderdeter v mined by the movements of the dial, the movements of thedial alsosimultaneously establishing a frequency on which conversationcan be carriedon, and a receiving. circuit which is responsive, at eachstation, onlyto a particular one of such sequences, whereby the signalofvonly that subscriber who is called will be operated. A g

4. A dial for use in radiotelephony, comcooperating with said dial,whereby upon partial rotation and return of said dial, only one of thecontacts is caused'to control a corresponding circuit, and other meansco,- operating with the dial, comprising a ratchet wheel, a pawl pivotedto the dial and engaging the teeth of said ratchet-wheel, and a.sec ondpawl to prevent the ratchet wheel from returning when the dial returnsto its normal position.

5. A dial for use in radio telephony, comprising a plurality ofcontacts, and means cooperating with said dial, whereby upon partialrotation and return of said dial, only one of the contacts iscaused tocontrol a corresponding circuit, and other means cooperating with thedial, comprising a ratchet wheel, a pawl pivoted toth'e dial andengaging the teeth of said ratchet wheel, and a second pawl to'preventthe ratchet wheel from returning when the dial returns to its normalposition, whereby'the ratchet wheel is moved to an extent equal'to thesum of the successive movements of the dial. V

6. In a radio telephone having a"tra ns mitting circuit, a dial having aplurality of contacts. a receiver hook, a switch'actuated thereby forcontrolling the transmitter cir cuit, and means cooperating with saiddial, whereby upon partial rotation and return of said diahonly one ofthe contacts is caused to control a corresponding circuit, and othermeans cooperating with the dial, comprising a ratchet ,wheel. a pawlpivoted to the dial and engaging the teeth of said ratchet wheel, and a.second pawl to prevent the ratchet wheel from returning whenthe dialreturns to its normal position, and means connected to and actuatedbythe receiver hook ,for releasing both pawls when the receiver isreturned to the hook, whereby the ratchet wheel will be capable ofreturning 'to its initial position. r

7. In a radio telephone having a transmitting circuit, a dial having aplurality of contacts, a receiver hook, a switch actuated thereby forcontrolling the transmitter circuit and means cooperating with saiddial, whereby upon partial rotation andfreturn of said dial, only one ofthe contactsfislcaused to control a corresponding circuit, and othermeans cooperating withthe dial, compris ing a ratchet wheel, a pawlpivoted to the dial and engaging the teeth of said ratchet wheel,

and a second pawl to, prevent the ratchet wheel from returning when thedial returns to its normalposition, and meanscon'nected to and actuatedby the receiver hookfor ref leasing bothlpawls when the receiver isreturned to the" hook wherebythe ratchet wheel will vbe capahleofreturning'toits 'initial position, and a spring for returningjthje saidratchet wheelto itsrsaid initial position. prising a plurality ofcontacts, and means 8 A for, use in radio-tclcphonypcomprising .a dischaving a series of notches therein, constituting ratchet teeth, Land; a

superposed ratchet wheel, aIpawl cooperat ing with the disc to, beactuated ioneof f the teeththereof, contact controlling means actuatedby said pawhand asecond pawl pivoted to thedisc and cooperating: withthe ratchet wheel, and a thirdpawl also'cooperating with thesaidratchetwheel-to retainit the second pawl.

in the position towhich it has been moved loy 9. 'A dial'for use inradio telephony, foo mtherein, constituting ratchet teeth Qandasuperposed ratchet wheel, a pawl 'cooper ating with the disc .tobegactuated one of the teeth thereof, .contactcontrolling: meansactuated by saidpawl, and a-secondgpawl :pivtit-Q oted to the disccooperating;withf the saidsecond and third paivls for engagement withthe ratchet wheel.

7 10. AV-dial foruse inradio comprising a disc, a ratchet wheelcooperating therewith, means whereby v disc shifts the ratchet wheel, ashaft .ci0ni1ected to the ratchet wheel, a doublearmedcontactgleveroperatedbysaid shaft rand a series ofustationary contacts cooperating;with th e ,said contact lever. r a

. 11. A dial for use in. radio telephony-seemprising a disc, aratchetwheel cooperating therewith, means wherebythe disc. shifts the ratchet:wheel, a shaft. connected to the ratchet wheel, a double armed contactlever;

operated byrsaid. shaft, series ofsta- 1 tionary Icontacts cooperatingwith the said contact lever, saidcontacts being so atranged that one endof the lever'will always 7 engage one of said contacts, 1 v a. 12. Asystem of radio telephone communication comprlsing a series ofsubscribers, stations, each station including manuallyfcom trolledtransmitting means for send ng 1111-,

pulses of predetermined frequencies in a prising a-dischaving a,seriesof notches given sequence at the will of the subscriber, and receivingmeans, the receiving .means comprisinga plurality of circuits tunedsynchronously with the'transniitted frequencies, and further comprisinga pluralityof interlocking relays which are operated when waves ofpredetermined length are received in a predetermined sequence, thetransmit-.

ting means being tunable,funder the control of the subscriber, so'thatit maybe caused to correspond to the wave length ofthe station withwhich communication is to be established, said tuning being accomplishedby the manual operation of the transmitting means.

13. A system of radio telephonic commu 'nication comprising a series of.subscribers stations, each having calling means capable of emitting asequence if impulses of certain fixed wave lengths, and in an orderdetermined by the calling subscriber, and a receiving circuit which isresponsive, at each station, only to a particular one of such sequences,whereby the signal of onlythat subscriber who is called will beoperated, the receiver circuit being permanently tuned to one of aseries of wave lengths, the designatingordinal of which is equal to thelast digit of the number representing the sum of the digits of thetelephone number assigned to the reciving station.

14. A system of radio communication,

comprising a series of subscribers stations,

each station including transmitting meansand receiving means,'thereceiving means of each station being arranged to respond'o-nly tocertain wave lengths sent in a particul'ar sequence, the sendingmeansof; each station comprising means for sending in succession a series ofwave lengths in a particular sequence, the sending station furthercomprisprising means for sending as the final wave of the series, atalking or carrier wave of a tion, as determined by thesequence ofsuccessive waves sent by particularly tuned.

15. A system of radio communication, comlar sequence, for establishingvcommunication with, and actuating a signal at, only the station of aparticular subscriber, the send mg station further comprlslng means forsending as the final wave of the series, a talking or carrier wave of awave length to which a certain receiving station, as determined by 'thesequence of successive waves sent by the sending station, isparticularly tuned.

thesending station, is

comprising a plurality of sending circuits I tuned to different wavelengths, and means, selectively and manually operated, for controllingthe operation of saidsendingbir uits, for sending a series of waveshaving wave lengths, and in a sequence, as determined by the movementsofsaid manually operated means. j

17. A system of radio communication,

comprising a series of subscribers stations wlthm'operat ve range'of oneanother, each station including transmitting means and receiving means,the receiving means of each station being arranged to cut in thatstation for operative communication only in response to adefinite'series of wave lengths sent in a definite sequence, the sendingmeans at each station comprising'a plurality of sending circuits tunedto difi'erent wave lengths, and manually operated meansfor'controllingsaid sendingcircuits, for sending a series of waves, having the desiredwave lengths, in the desired sequence.

18. A-syster'n ofradio communication, compr1s1ng a series of subscribersstations within operative range of one another, each station mcludingtransmitting'means and recelving means, the receiving means'of eachstation being arranged to cut in that station for operativecommunic'ation only in I response to a definite series of'wave lengthssent in a definite sequence, thesending means at each station comprisinga plurality of sending circuits tuned to different wave v I lengths anda manually controlled dial for wave length to which a certam receivingsta- 1 controlling the sending circuits, for sending,

inthe desired sequence, a series of waves of the desired wave lengths;:-V

Y 19. In a radio telephone, switch means for closing a' plurality ofcircuits in succession, a tuning device-in each of said circuitscontrolled by said switch means, a dial, selectively and manuallyoperated and operatively connected with the switch means, for closingthe several circuits controlled by said switch means in a sequencedependent upon the operation of. the dial, and transmitting meanscooperating witheach of the tuning circuits, whereby a particularsuccession of radio waves is-sent by saidtransmitting means, asdetermined bythe movements of the dial and its associated switch means.

20. In a radio telephone, switch means for closing a plurality ofcircuits insuccession, a tuning device in each of said circuitscontrolled by said switch means, a dial, selec tuning circuits, and withthe ringing signal circuit, whereby a particular successlon of radiowaves, followed by a ringingsignal, is

sent by said transmitting means, as determined by the movements of thedial and its associated switch means.

In testimony whereof I alfix my signature.

HERBERT S. POLIN.

